The concept of covert communication in optical domain and its performance estimation indexes of imperceptibility, usability, and robustness were illuminated. The method of optical domain covert communication based on coherent optical code division multiple access (OCDMA) technology was analyzed. Three covert schemes and their system configuration parameters were offered. Aiming at the properties of existing optical communication host channel, code-shift-keying (CSK) balance modulation and double side band en/decoder based on equivalent phase shift-superstructure fiber Bragg grating (EPS-SSFBG) were proposed to improve the performance of the system. The simulation results show that the proposed schemes can obtain a good performance. With signal-to-noise rate (SNR) of -13 dB, under the condition that the signal was completely covered by channel noise, and in this situation, the system still kept communication with a bit rate of 1.25 Gb/s, the inter-influence between covert signal and host signal was suppressed.